wait_for_async_assigns

Prevents "DBConnection.ConnectionError: client exited" errors in Phoenix LiveView tests

Installation

Add to your mix.exs:

def deps do
  [
    {:wait_for_async_assigns, "~> 0.1.0", only: :test}
  ]
end

Import in your test case module (e.g., test/support/conn_case.ex):

defmodule MyAppWeb.ConnCase do
  use ExUnit.CaseTemplate

  using do
    quote do
      import Phoenix.ConnTest
      import Phoenix.LiveViewTest
      import WaitForAsyncAssigns

      @endpoint MyAppWeb.Endpoint
    end
  end
end

Import the formatter config in .formatter.exs:

[
  import_deps: [:phoenix, :wait_for_async_assigns],
  # ...
]

Usage

Call wait_for_async_assigns/1 at the end of LiveView tests that use async operations:

test "loads data asynchronously", %{conn: conn} do
  {:ok, view, _html} = live(conn, ~p"/products")
  html = render_async(view)
  assert html =~ "Products"

  wait_for_async_assigns(view)
end

The function waits for all async tasks to complete before the test exits, preventing connection errors.

Custom timeout:

wait_for_async_assigns(view, 10_000)  # Wait up to 10 seconds

Default timeout is 100ms (configurable via config :ex_unit, assert_receive_timeout: 1000).

Optional Credo Check

This package includes a Credo check that warns when LiveView tests are missing wait_for_async_assigns/1.

Add to .credo.exs:

%{
  configs: [
    %{
      name: "default",
      requires: ["deps/wait_for_async_assigns/lib/credo/check/wait_for_async_assigns.ex"],
      checks: %{
        enabled: [
          {Credo.Check.WaitForAsyncAssigns, []}
        ]
      }
    }
  ]
}

Resources

• Phoenix LiveView Issue #3545

License

MIT License - see LICENSE for details.

Contributing

Contributions are welcome! Please open an issue or pull request on GitHub.

Credits

Created by Mario Uher.